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Discussion Starter · #1 · (Edited)
I searched for this answer and could not find it. I am not sure which brand of furnace I have. When I opened the cover it says the model number is G1N80AT100D14B-2. My furnace works great on heat. Now that it is hot outside I would like to run the fan setting to get some extra circulation in the house. I don't have A/C. How do I hookup my furnace to only operate the fan? I tried using the "on" setting on the thermostat on both the heat and cool setting but that didn't work. I am a novice so please walk me step by step. I am hoping I just switch one of the jumpers on the circuit board. By the way, I don't believe that my thermostat is even hooked up to the cool setting at all. Thanks in advance!
 

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If your furnace is for heating only, chances are that you do not have the wiring present for a fan relay to operate. How many wires are present on that thermostat? 2? 3? 4 or more?

Most heating only furnaces operate the fan by use of a heat activated limit switch. In other words, you can't run the fan unless the furnace gets "hot" --- and you don't really want to go there in this weather!!

:whistling2:
 

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Heat/Cool/Off set to Off, and Fan/Auto set to Fan. What is the manufacturer of the furnace, and is it powered up right now (ie breaker not shut off during cooling season). If you rent, call management. As for running the fan, it will move some air, but will do nothing compared to what central a/c would do.
 

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Discussion Starter · #5 · (Edited)
I have three wires in the back of the thermostat, but only two are connected. One is red hooked up to the R and the RC of the thermostat with a jumper. The other wire is blue connected to the W of the thermostat. I have a white wire not connected... Maybe it connects to the G of the thermostat to run the fan? My furnace is a Armstrong Ultra V Tech 80.
 

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If your furnace control board has a ‘G’ terminal, connect the un-used white wire to it, and to the ‘G’ terminal at the stat, then try it and see if the fan runs (it should).

Be aware that the white wire may be broken inside the sheath somewhere. Usually the white wire is connected to ‘W’ at the stat and furnace. No reason other than consistency. But since someone didn’t use it before, it might have been broken, so they had to use the blue for ‘W’.
 

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Discussion Starter · #9 ·
Yes, I do have the furnace manual. It doesn't really help. It just says to turn the thermostat to fan on.
I am willing to try the white wire in the G of the thermostat, but will I screw up anything if it is the wrong wire? I am not really willing to take a chance to fry the circuit board. That would be bad!
 

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There should be a on/off switch near the furnace for servicing it. Turn it off and take off the door panel(s) to access the circuit board. If the white wire isn’t hooked up to anything, hook it up to ‘G’, then hook it up to the stat ‘G’. Put the door back on and turn it on, it should work.

Standard forced air furnaces….R=24v feed (to stat) W=heat mode G=fan on Y=cooling mode
 

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Discussion Starter · #11 ·
The white wire that is not connected is behind my thermostat not furnace. There are many white wires hooked up to the circuit card of the furnace so I can't tell you which one it is...
 

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There should be a spot on the circuit board with a set of screws that match the screws for your thermostat. If unsure, post a picture.
 

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In the furnace on the control board, the stat wires are going to be: red hooked to ‘R’, blue to ‘W’. These are the colors you said are hooked to the t/stat. Find the white of that same cable in the furnace.
 

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On the second picture, there are screw terminals with smaller wires connected....I see a white and red wire.....any others connected to those screws?
 

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With that connection, you have heat only, and fan on heat rise available. The fan switch cannot work as wired.
 

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Unfortunately no. You need another wire to connect the terminals between the control board and the stat...if the furnace is wired for it. Can you see behind the terminal screws where (if anywhere) the wires go from the g terminal?
 

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Discussion Starter · #20 ·
Unfortunately no. You need another wire to connect the terminals between the control board and the stat...if the furnace is wired for it. Can you see behind the terminal screws where (if anywhere) the wires go from the g terminal?
I'm not following. Can I see the back of the thermostat where the G terminal is?
 
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